<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>

<body>
<!--
    http://localhost:8080/58/userServlet?username=admin

    请求体：
           username=admin

-->

<form method="post" action="userServlet">
    用户名：<input type="text" name="username"> <br>
    <input type="submit" value="校验">
</form>

</body>
</html>